The HIV-1 nef protein inhibits extracellular signal-regulated kinase-dependent DNA synthesis in a human astrocytic cell line.
The role of nonproductive infection of astrocytes by human immunodeficiency virus type 1 (HIV-1), characterized by the overexpression of nef, in brain disease progression is largely unknown. We investigated the consequences of stable expression of nef from the HIV-1 strain LAI in the human astrocytic cell line U373. DNA synthesis induced by endothelin-1 (ET-1) was largely decreased by nef. Stable expression of nef did not affect the ET-1-induced tyrosine phosphorylation of focal adhesion kinase, an adhesion-dependent pathway known to participate in DNA synthesis in astrocytes. Conversely, the activation of extracellular signal-regulated kinase (ERK) by ET-1 was largely inhibited in cells stably or transiently expressing nef. A similar inhibitory action of nef on ERK activation was observed after direct stimulation of G proteins. Furthermore, the inhibitory action of nef did not require protein kinase C (PKC) and affected mainly the PKC-independent pathway of ERK activation. Following chemokine receptor CXCR4-mediated infection of U373 cells stably expressing CXCR4 with the T-tropic HIV-1 strain m7-NDK, ET-1-induced activation of ERK was also inhibited. Altogether, these results indicate that intracellular signaling pathways associated with the growth factor activity of ET-1 are impaired in nef-expressing and HIV-1-infected astrocytes, suggesting that infection of astrocytes may play a significant role in the neuropathogenesis of HIV-1 encephalopathy.
Romero
I A
IA
CNRS UPR 0415, Institut Cochin de Génétique Moléculaire, Paris, France.
Teixeira
A
A
Strosberg
A D
AD
Cazaubon
S
S
Couraud
P O
PO
D001253:Astrocytes / Q000378:metabolism*; D001254:Astrocytoma; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002460:Cell Line; D004261:DNA Replication / Q000187:drug effects*; D019332:Endothelin-1 / Q000494:pharmacology*; D004789:Enzyme Activation; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D015693:Gene Products, nef / Q000096:biosynthesis / Q000378:metabolism*; D015497:HIV-1 / Q000502:physiology*; D006801:Humans; D019950:Mitogen-Activated Protein Kinase 1; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D054398:Receptors, CCR4; D019707:Receptors, Chemokine / Q000096:biosynthesis; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D014162:Transfection; D054311:nef Gene Products, Human Immunodeficiency Virus
C515354:CCR4 protein, human; D015815:Cell Adhesion Molecules; D019332:Endothelin-1; D015693:Gene Products, nef; D054398:Receptors, CCR4; D019707:Receptors, Chemokine; D011994:Recombinant Proteins; D054311:nef Gene Products, Human Immunodeficiency Virus; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1